[Tooth movement in class II division 1 malocclusion after premolar extraction].

OBJECTIVE: To investigate the magnitude and pattern of tooth movement in class II division 1 malocclusion cases treated with extraction of upper first and lower second premolars. METHODS: Thirty cases of class II division 1 malocclusion were examined with pre- and post-treatment lateral cephalometric radiographs. The movement of both front and posterior teeth, on both upper and lower jaws were measured and compared. RESULTS: The crowns of the upper and lower central incisors moved distally for (3.59 +/- 2.39) mm and (2.32 +/- 1.58) mm, respectively. The root apexs moved distally for (1.19 +/- 2.44) mm and (1.56 +/- 0.98) mm. The labial inclinations of the upper and lower central incisors decreased by 9.87 degrees +/- 7.68 degrees and 2.64 +/- 3.99 degrees. The crowns of the upper and lower first molars moved mesially for (4.32 +/- 4.87) mm and (4.38 +/- 1.46) mm, respectively. The buccal root apexs moved mesially for (2.74 +/- 1.56) mm and (4.43 +/- 2.12) mm. The upper and lower first molars rotated 3.90 degrees +/- 4.55 degrees and 1.25 degrees +/- 6.06 degrees counterclockwisely. The changes were statistically significant (P<0.05). CONCLUSION: The ratio of front and posterior teeth movement is 1 : 1.3 for maxillary teeth and 3 : 5 for mandibular teeth. Upper incisors move as controlled tipping and lower incisors exhibit bodily movement.